Intracranial neural interface system

ABSTRACT

In some preferred embodiments, without limitation, the present invention comprises an implantable, intracranial neural interface node which is an integrated and minimally invasive platform system and supports cross-modal neural interfaces to the cerebrum and other associated structures in the central nervous system. The neural interfaces comprise electrical and chemical interfaces for neural recording, electrical stimulation, chemical delivery, chemical sensing, chemical sampling, cell delivery, genetic material delivery and/or other functions of interest.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority based on U.S. Provisional PatentApplication No. 60/513,035, filed Oct. 21, 2003, which is herebyincorporated by reference in full.

FIELD OF THE INVENTION

The present invention relates generally to systems, methods, and devicesfor interfacing with neurological systems.

BACKGROUND

Among researchers, clinicians and others, there is increasing interestin neural interfaces which may allow the transmission of informationrelating to neural activity, or delivery of therapeutic substances, toand from neurological systems. Some interfaces, such as corticalinterfaces, show much promise for use in brain-machine interfacesystems, whether for purposes of accessing or delivery of chemical orbiological substances or electrical signals, or for controlling oraffecting machine or information system activities.

Implantable microelectrodes for such purposes have received increasingattention from interested persons, especially as biomaterials and thetechnology of microscale probes and electronics have improved. Thus, anunmet need remains for small scale neurological interfaces such as thosecomprising the present invention.

SUMMARY OF THE INVENTION

In some preferred embodiments, without limitation, the present inventioncomprises an implantable, intracranial neural interface node which is anintegrated and minimally invasive platform system and supportscross-modal neural interfaces to the cerebrum and other associatedstructures in the central nervous system The neural interfaces compriseelectrical and chemical interfaces for neural recording, electricalstimulation, chemical delivery, chemical sensing, chemical sampling,cell delivery, genetic material delivery and/or other functions ofinterest.

In some preferred embodiments, without limitation, the invention iscomprised of two or more elements, including an approximatelycylindrical housing that is inserted into the cranium, one or moremicro-scale neuroprobe assemblies that provide electrical and/orchemical interfaces to specific brain regions, one or more electroniccomponents for instrumentation and signal conditioning, and/or one ormore fluidic components for transmission of fluids, cells, gels, geneticmaterial or other chemical or biological substances.

Other aspects of the invention will be apparent to those skilled in theart after reviewing the drawings and the detailed description below.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described, by way of example only,with reference to the accompanying drawings, in which:

FIGS. 1(A)-(C) are respectively: (A) a three-dimensional schematicdiagram of a cranial platform and layout of electronic subsystems withina skull base station; (B) a cut-away view of an inserted intracranialchamber; and (C) a view from within an inner lumen showing theprotrusion of a neuroprobe assembly into the cortex.

FIG. 2 is an illustration of one embodiment of the invention, withoutlimitation.

FIG. 3 is a photograph of one embodiment of the present invention,without limitation, with four silicon neuroprobes.

FIG. 4 is a layout of a microelectrode in accordance with oneembodiment, without limitation.

FIG. 5 shows a detailed view of a connection between the siliconneuroprobes and the printed circuit board of an electronics interface ofone embodiment, without limitation

Other aspects of the invention will be apparent to those skilled in theart after reviewing the detailed description below.

DETAILED DESCRIPTION

The invention comprises an integrated microsystem for creating aminimally invasive, microscale, multichannel neural interface for neuralrecording, stimulation, and/or delivery or uptake of drugs or othersubstances. In some preferred embodiments, without limitation, theintracranial neural interface node of the present invention comprises(i) an implantable intracranial chamber, optionally including a coverand/or a lumen plug, (ii) electronics and/or fluidic interface, as oneexample only, a rim circuit board, and (iii) neural interfaceelectronics.

The intracranial chamber, or cranial platform, serves several functionsin the invention. Among others, it provides a method to permanentlyocclude the cranial defect that results from the surgical burr hole andto seal the dura incision that results from exposing the corticalsurface. It also provides a sealable package to house the electronicsinterface of the device. In addition, it provides a structure forpackaging neuroprobe assemblies so that they can be reliably andefficiently manipulated and implanted by the neurosurgeon or otherclinician in the operating room environment.

In some embodiments, the invention comprises a skull platform thatutilizes the relatively generous dimensions afforded by the burr hole,the relatively thick skull, and the superior cranial surface surroundingthe burr hole. The design or dimensions of the chamber or lumen isconstrained by the neurosurgeon's need to visualize and manipulate theneuroprobe assemblies after the housing is located in the cranium.

The cross-modal interface system comprising the invention is capable ofmultiple modes of interaction with the brain and can interface withneural tissue on the spatial scale of nominally 1 micron to 1 cm. Theinvention comprises a device which interfaces with the brain with a highdensity of recording/stimulation sites in a target area of the brain,with appropriate system complexity to enable low-power embedded signalprocessing and wireless data transmission and a modular design thatuncouples the neuroprobe design from the electronics interface andpackaging designs, while allowing minimally-invasive access to the brainthrough the surgical burr hole in the skull.

In some preferred embodiments, the invention comprises a hollowintracranial chamber of approximately circular cross-section that issized to fit in a surgical burrhole that is typical for accessing thehuman cerebral cortex. Such burr holes may be between 0.5 and 2.0 cm,although other sizes may also be used at times. In some embodiments, thetop surface of the chamber is flush with the cranial surface, and thebottom surface extends part way through the cranium. The chamber mayhave a shelf for placement of the electronics interface. The chamber,and/or a corresponding lid, where desired, may be constructed frompolysulfone, a machinable and biocompatible polymer, titanium, or othersuitable plastic or metal material known to those of ordinary skill inthe art.

FIG. 1 shows one embodiment of a intracranial chamber or platform 1,without limitation. In this embodiment, the platform is comprised of twocomponents, a top 7 and a skull plug component 27, that are machinedfrom titanium and joined by a flexible multi-wire ribbon cable 11. Theskull insert component 27 is milled from single stock to have anapproximately 1.8 cm diameter cylindrical base with an open lumen 35 anda 2.5 cm diameter top flange 23. The flange is machined to have a recesson the top side that may house printed circuit boards 3. One or moregrooves 34 (FIG. 1(C)) may be machined in the side walls of the innerlumen 35 to allow the passage of the flexible interconnect cable 33 fromthe bottom of the skull insert 27 to the printed circuit boards 3 at thetop.

The top component 7 may also include a recess on its top to accommodatean RF coil 13 as well as a deeper recess in the center of the lumen plug25 to house internal telemetry circuit components 15, where desired.

As illustrated in the embodiment of FIG. 1, the electrode 5 and flexibleinterconnect 33 subsystem attaches at the bottom of the base stationplug 27, the signal conditioning subsystem electronics 19, 21 arelocated on the top of the base station platform 23, the telemetryelectronics 15 reside in the lumen plug portion 25 of the base stationtop 7, and the RF coil 13 is embedded in the base station top 7.

Application-specific mixed-signal chips may be configured on a rimcircuit board 3 that is machined to fit the annular structure of theskull insert. In some embodiments, without limitation, the invention maycomprise one or more analog integrated circuits 19 for amplification,filtering, and/or multiplexing, and/or one or more digital integratedcircuits 21 for data compression, signal feature detection, and/ortelemetry.

The corresponding plug (FIG. 1) provides a conceptual layoutillustrating multiple dies integrated onto a single circuit board. Thecircuit areas 3 on the top of the skull insert 27 and in the plug 7 areadequate for the chipset required for an intracortical interface node.This invention facilitates chip-level testing before the circuits andconnectors are irreversibly sealed. The circuit boards for the twocomponents may be connected with a flexible ribbon cable 11 to allow theplug to be folded and inserted into the lumen 35 of the skull insertduring the intraoperative procedure without making new electrical ormechanical connections.

The intracranial chamber is inserted into a surgical burr hole in thecranium at a position roughly overlying the targeted neural structure.Without limiting the invention to a particular size or shape, the uppersegment of the burr hole may have a larger diameter than the lowersegment, with either a stepped or approximately tapered profile. Theupper diameter may be in the range approximately 0.8 cm to approximately2.5 cm and the lower diameter may be in the range of approximately 0.5cm to approximately 2.3 cm. The transition between the two segments isin the range of approximately 0.3 cm to approximately 0.6 cm from thetop surface of the cranium. The bottom surface of the device may beapproximately flush with the bottom side of the cranium to provideaccess to the dura mater 31. The dura mater may be incised by theneurosurgeon to expose the surface of the cerebral cortex although thedura membrane might not be incised for some applications. The uppersurface of the device is approximately flush with the top surface of thecranium and may be shaped to follow the local contours of the cranium.

The housing material is comprised of one or more biocompatible polymersor metals. In some embodiments, without limitation, its outer surface isof a material and composition that promotes osseointegration tostabilize the housing in the cranium. The depth of the housing may bealtered at the time of surgery to accommodate variable cranialthickness.

FIG. 2 is an illustration of another embodiment of the invention,without limitation. In this embodiment, the invention comprises a hollowintracranial chamber 1 of approximately circular cross-section that issized to fit in a surgical burrhole that is typical for accessing humancerebral cortex. The top surface of the chamber 1 is flush with thecranial surface, and the bottom surface extends part way through thecranium 29. The chamber may have a shelf 9 for placement of theelectronics interface 3. The device may also have a lumen plug 25 thatis threaded and screw fit to seal the device. The electronics interfacecomprises an interface board 3, as one example only, a printed-circuitboard, which contains integrated circuits for signal conditioning andsignal processing of the neural signals recorded by the implantedmicroelectrodes 5. The circuit may contain RF circuitry 26, as oneexample only, for inductive power, as well as application-specificcircuitry 28. The neuroprobe assemblies comprise separate siliconmicrofabrication microelectrode arrays 5 that are individuallymanipulated and inserted into the brain and connected via interconnects33 to the electronics interface 3. The site layout of the microelectrodearrays 5 is general in this illustration but may be optimized for use inparticular regions of the brain. Each probe 5 is connected to theelectronics interface 3 through a microfabricated interconnect cable 33.

In some embodiments, a segment of the chamber might extend to the topsurface of the cranium. The walls of the chamber may not extend all theway to the lower surface of the cranium. The exterior walls of thechamber may also comprise a material to inhibit bone regrowth around theedge of the chamber. The upper and lower lumen sizes can vary (nominalrange between 3 mm and 2.5 cm diameter). There might be wires and/ormicrocapillaries extending out of the chamber to additional devices orstructures.

In some embodiments, the chamber includes a closely fit cover for thetop surface. This cover might be screwed into the chamber or seated on aclosely fit seals. It is intended to provide a hermetic seal of thechamber.

FIG. 3 is a photograph of one embodiment of the invention, withoutlimitation to a single embodiment. This embodiment has siliconneuroprobes (not shown) with interconnects 33, shown here within thelumen 35 of the device. The electronics interface 3 has straight-throughconnectors 43 rather than integrated circuits. The circuit board ispermanently attached to the intracranial chamber 1, with the top surfacesealed and electrically insulated with epoxy (represented by gloss areaover interface 3). The lumen 35 is filled with a hydrogel polymer 37.

In some embodiments, the invention comprises a lumen plug that isinserted into the lumen of the intracranial chamber to seal the braincompartment from the chamber compartment. The lumen plug may becomprised of a biocompatible polymer that accommodates and seals theinterconnects that may extend between the brain compartment and chambercompartment. The plug may include both a plug material and a polymersealant that is applied around its edges. In some embodiments, the plugmay be of a material that cures or otherwise changes conformation due toultraviolet light, heat, or other types of catalysts. It may alsocomprise a combination of soft and hard polymers.

In some embodiments, the lumen plug may comprise one or more components,as one example only and without limitation: (i) a biocompatiblehydrogel, as one example only, an alginate, in contact with the brainand dura that eventually interacts with the tissue to form a hydrostaticseal between the brain compartment and the chamber compartment; (ii) asilicone elastomer or other suitable known to those of ordinary skillthat fills all or a portion of the remaining volume of the lumen; and(iii) a lumen cover that forms a tight seal around the edge of thelumen, as some examples only, a polymethylmethacrolate or polysulfonecover or lid.

In some embodiments, without limitation, the invention compriseselectronic and/or fluidic elements that may be located in theintracranial compartment to provide instrumentation, signal processing,and/or fluid processing functionality. The electronic elements may beplaced on one or more printed circuit boards. In some embodiments, eachboard is flat and approximately circular with an open center to maintainthe central lumen of the chamber. Multiple boards may be stacked in thechamber. The boards may be rigid or flexible. In other embodiments, oneor more flexible circuit boards may be placed on the inner wall of thechamber. The bottom side of the lowest board may be seated on thechamber ledge. Optionally, a node may not have any active electronics inits electronics interface.

In some embodiments, without limitation, the invention may comprise oneor more low-power chips to implement stages of on-board signalprocessing such as: (i) analog front-end electronics, (ii) real-timesignal compression, and (iii) short-range telemetry. Such embodimentsreflect a conservative and robust approach for implementing therequisite real-time neural signal processing. In some embodiments, theneural interface electronics are designed and/or selected to transmitthe raw neural signals to an external, programmable real-time signalprocessor for analysis (e.g., for spike discrimination, neural featureextraction, and adaptive decoding). Embodiments of the inventioncomprise many of the advantages of on-board signal processing (e.g.,amplification, site selection, wireless transmission) while alsoproviding maximum flexibility in developing optimal algorithms toextract the relevant control information from the recorded spiketrains.At the same time, the invention comprises a solid platform that isadaptable to known and developing signal processing requirements ofreal-time cortical control in mammals.

In some embodiments, the neural interface electronics architecture ofthe invention may use a mixed-signal chipset at the user's choice. Assome examples only, an analog integrated circuit (“IC”) may provideamplification, filtering, analog/digital (“A/D”) conversion, andfront-end selection (multiplexing) for 32 channels of extracellularrecordings. A digital IC implements spatial filtering, sub-bandfiltering, thresholding, and coding operations to provide real-timelossless signal compression. In some embodiments, a completeintracortical interface node having 128 sites may use four analog ICsand one digital IC. This implementation is advantageous because itallows the signal processing circuitry to be implemented with thesmaller feature sizes and supply voltages of a modern digital circuitprocess; these digital processes are not compatible with the increasedsupply voltages and the high quality transistors that are required toimplement reliable amplifiers and A/D converters (ADCs) appropriate forneural signal processing.

In some embodiments, the invention comprises a wireless communicationchannel for the intracortical interface node which (i) receives controldata from an external control system, (ii) transmits compressed anddigitized neural signals across the transcutaneous link, and (iii)supplies power to the implanted electronics. A telemetry receivercircuit may be included which is external to the subject, as one exampleonly, packaged in a “Walkman-like” headband designed to position thereceiver on the skin overlying the implanted transmitter coil.

In some preferred embodiments, without limitation, the inventioncomprises one or more neuroprobe assemblies comprised of one or moremicro-scale devices that are inserted into or placed onto the brain toestablish chemical and/or electrical interfaces to specific neuraltargets. Without limitation, some embodiments of the invention comprisethe connection, integration and/or use of various combinations of thesetypes of devices to result in a particular method to create anintegrated cross-modal neural interface. The electrodes may bepositioned on the surface of the brain, on the dura, or otherwise sitedaccording to the user's choice. A combination of penetrating electrodesand surface electrodes may be used. The electrodes may be combined withone or more fluid delivery probes that either penetrate the brain orremain outside the parenchyma.

Some embodiments of the invention comprise the connection of multipleneuroprobe assemblies to an intracranial signal and fluidic processingnode. In one embodiment, without limitation, an invention may includefrom 1 to 5 neuroprobe assemblies per node. Neuroprobes in someembodiments may be connected to the electronic and/or fluidic processingelements through flexible interconnects that transmit the appropriateelectrical signals or fluidic channels.

In some embodiments, the neuroprobe assemblies are composed ofsilicon-substrate microelectrode arrays that are connected to the rimcircuit board through flexible microfabricated ribbon cables, orinterconnects. In some embodiments, a device comprising the inventionmay contain 4 to 6 separate 32-channel neuroprobe assemblies that areregularly positioned around the lumen of an annular rim circuit board,which may have a nominal lumen diameter in some embodiments of 0.5 to 2cm.

The invention comprises more system complexity in a smaller package or“footprint” than any existing device, with packaging and bonding suchthat separate microelectrode arrays can be individually placed within asmall volume of the brain. The use of the intracranial chamber forhousing system components reduce the level of invasiveness. The use ofan annular circuit board in some embodiments provides a central accessto the brain surface, while retaining system complexity andlow-footprint device. Moreover, bonding the multicontact probes to theinterface board reduces the lead complexity to enable high-channel countsystems. The invention also allows direct visualization of the insertionof the probes by the surgeon or clinician in order to avoid surfacevasculature.

In some embodiments, the silicon microelectrode of choice is a32-channel device with four penetrating shanks (FIG. 4), with designfeatures selected based on published human anatomical data. FIG. 4 islayout of a microelectrode 39 in accordance with one embodiment, withoutlimitation. The shanks of this embodiment are 25 millimeters×107millimeters in cross-section and terminate in a relatively sharp tip. Avariety of different site areas 41, ranging from 200 to 1000 μm², may beincluded to affect recording quality as it relates to site area. The tipshape is based on successful insertion tests in fresh human cadaverbrain. Typical penetrating shanks have cross-section dimensions of 15×60microns and length of the penetrating shank of 2-3 mm.

In some embodiments, the invention may comprise one or more so-called“Michigan probes,” a particular type of microfabricated siliconsubstrate microelectrode known to those of skill in the art. See e.g.,Hetke, et al., “Silicon microelectrodes for extracellular recording” inW. E. Finn (ed.), Handbook of Neuroprosthetic Methods (Boca Raton, Fla.:CRC 2002). This probe has several favorable attributes including batchfabrication, reproducibility of geometrical and electricalcharacteristics, easy customization of recording site placement andsubstrate shape, small size, and the ability to integrate it with asilicon ribbon cable and to include on-chip electronics for signalconditioning. The extensibility of the platform technology also enablescustom designs for diverse applications. For example, planar probes havebeen assembled into multiplanar arrays for precise three-dimensionalplacement of recording sites in the brain, and the probes have beencombined with a polymer ribbon cable to form a hybrid assembly toprovide additional mechanical flexibility. Probe designs includemicrochannels along the shanks for microscale and controlled fluiddelivery through the blood brain barrier. These silicon probes arecurrently used by many investigators and are now well validated forrecording both spike activity and field potentials in diverse brainstructures over acute and semichronic time durations up to severalweeks. The probes have been found reliable for recording multichannelspike activity and local field potentials over studied time periods,thus demonstrating the feasibility of using the probe in an implantablemicroscale chronic intracortical neural interface for medicalapplications, including cortical prostheses, like those comprising thepresent invention. In some embodiments, without limitation, themicroelectrode of choice is a polymer-substrate microelectrode of a typedescribed in P. J. Rousche, D. S. Pellinen, D. P. Pivin, Jr., J. C.Williams, R. J. Vetter, and D. R. Kipke, “Flexible polyimide-basedintracortical electrode arrays with bioactive capability,” IEEE TransBiomed Eng, vol. 48, pp. 361-71 (2001).

FIG. 5 shows a detailed view of a connection between the siliconneuroprobes and a printed circuit board 3 of an electronics interface ofone embodiment, without limitation In this view, the device has not yetbeen placed in situ. Two of six 4-shank probes 5 can be seen in thetop-left region of the view are attached to the board at their other end(out of view). Interconnects 33 for the probes are also shown in part inthe lumen 35, with the shinier colored interconnects 33 leading toprobes folded on top of the device before placement, and the darkercolored interconnects attaching to probes (not shown) folded underneaththe plane of the circuit board 3. A bond-pad region 42 of a separateprobe is seen at the center of the photo. The individual traces of theprobe are attached to the board using wirebonds and then sealed withepoxy (represented by gloss areas on circuit board 3).

The interconnects provide mechanical, electrical, and/or fluidicconnections between the probe assembly and the rim circuit board. Theinterconnects may be flexible in order to minimize tethering forces onthe brain, comparable in size to the scale of the probe assembly, andmechanically robust to withstand surgical manipulation. As one exampleonly, one type of interconnect comprising the invention is a siliconribbon cable which can be integrated directly with the back end of theprobe. Choice of the interconnect design can also improve mechanicalstability. For example, meandering (i.e. zigzagging) andmicrofabrication with silicon or polymer and slotting of the cables mayimprove resistance to breakage during twisting and in-plane bending,flexibility, and strain relief

An alternative interconnect is a microfabricated polymer ribbon cable.Polyimide is a desirable cable substrate due to its flexibility, processcompatibility, mechanical robustness, and biocompatibility. The polymercables can be constructed of alternative polymers such as parylene orliquid crystal polymer. Additional insulation to the polyimide cablesmay be added with an underlying layer of silicon dioxide and a top layerof silicone. Liquid silicone rubber may be spun on (or possiblydeposited using PECVD) and cured and either dry-etched and/or laserablated to open contacts and clear the field regions. A backside etchmay be performed in hot 20% KOH to dissolve the silicon wafer carrierand the devices removed from their frame using a laser. The design ofthe polyimide cables may be adapted by slitting in between the metalleads, permitting silicone to flow between them and consequently inhibitleakage between leads.

In some embodiments, without limitation, the probe assembly andinterconnect may be fabricated of similar materials so that they areintegrated and no separate connector is required.

In some embodiments, without limitation, the invention comprises one ormore integrated fluidic elements in the chamber in order to manipulateand control fluid delivery and/or sampling to the neuroprobes. Theseelements may be integrated in or placed on separate boards in thechamber. Alternatively they may be attached to the intracranial chamber.These elements may include, without limitation, valves, flow meters,pumps, pressure sensors, optical sensors, and reservoirs. Some of theseelements may be controlled with electrical signals. The electronics andfluidic interface may be located in the intracranial space or on thesurface of the cranium. The electronics interface board may beintegrated with flexible interconnects (leads) to the neuroprobes. Theinterface may contain a combination of active electronic components. Theinterface board may contain fluid control components, such as valvesand/or pumps. The interface board may not be uniformly planar (flat),having vertical, slanted, or curved components. The electronic interfacemight involve a microprocessor for signal processing, including datacompression or feature coding.

The invention provides a minimally invasive neurosurgical method forcreating a chronic neural interface that has the system complexity foradvanced therapies, as one example only, for recording from a pluralityof sites. It invention comprises a modular and scalable architecturethat can be used to establish short-term or chronic neural interfacesfor neural recording, electrical stimulation, or microscale drugdelivery. As some examples only, embodiments of the invention may beused to acquire control signals in a cortical prosthetic system, forcortical microstimulation for treatment of pain, and for localized drugdelivery to brain tumors for chemotherapy.

This invention comprises the first known, fully implantable, cross-modaldevice for chronically recording from neurons in the nervous system. Itis a fully implantable device, without any transcutaneous components,and allows for multiple modes of operation (electrical recording,stimulation, chemical delivery, chemical sensing, stem cell delivery,gene delivery, etc). It is minimally invasive and replaceable if theunit is damaged or fails.

In practice, the clinician may use more than one intracranial interfacenode per patient. Multiple nodes may be connected either physically orthrough wireless telemetry. A node might be connected to one or moreexternal devices or implanted devices elsewhere on the body throughphysical or wireless connections. A node might include sensors of otherphysiological signals, such as electrocardiogram.

For a number of medical applications, one may wish to implant nodes ineach hemisphere. For example, in cortical neuroprostheses it would bebeneficial to record/acquire signals from motor cortex in eachhemisphere of the brain. Another example, for deep-brain stimulation(“DBS”), it would be useful to use a node to record in motor cortex toprovide feedback for neurostimulation. In this case, the DBS electrodewould be implanted through a separate burr hole. In both of these cases,the recording nodes would connect with either external or implantedmicroprocessors.

EXAMPLE

A probe was populated with six 16-ch. 4 mm 200 chron probes (1250 um²sites). A 10 mm trephine was used to create a craniotomy in the testsubject, a monkey. The dura was completely removed exposing the brainthroughout the entire craniotomy. After removal of the dura, a layer ofagar was administered over the cortex via syringe, which filled theentire craniotomy. The agar thickness was approximately 3 mm. A thinlayer of Kwik-Sil (elastomer polymer, WPI) was applied around theperimeter of the craniotomy prior to placement of the interface. Thisaided in sealing off the brain from the external environment. Theinterface was positioned over the craniotomy, with the inner lumen ofthe interface resting on op of the agar. It was cemented into place withdental acrylic and the ground wire was attached to two bone screws. Theprobes were implanted one at a time through the agar into the cortex.Once all six probes were inserted, the inner lumen was filled withKwik-Sil such that the entire ribbon cable of each probe wasencapsulated with the polymer. Dental acrylic was applied over theKwik-Sil to provide protective rigid coatings. Results showed thatneural recordings were present in all recording arrays (16-ch. Arrays)which penetrated the agar 24 hours post-implant. It was determined thatthe average impedance on the electrodes showing unit activity wereapproximately 400 kohms (measured with a system using a 1 kHz signal,manufactured by BAK).

While the present invention has been particularly shown and describedwith reference to the foregoing preferred and alternative embodiments,it should be understood by those skilled in the art that variousalternatives to the embodiments of the invention described herein may beemployed in practicing the invention without departing from the spiritand scope of the invention as defined in the following claims. It isintended that the following claims define the scope of the invention andthat the method and apparatus within the scope of these claims and theirequivalents be covered thereby. This description of the invention shouldbe understood to include all novel and non-obvious combinations ofelements described herein, and claims may be presented in this or alater application to any novel and non-obvious combination of theseelements. The foregoing embodiments are illustrative, and no singlefeature or element is essential to all possible combinations that may beclaimed in this or a later application. Where the claims recite “a” or“a first” element of the equivalent thereof, such claims should beunderstood to include incorporation of one or more such elements,neither requiring nor excluding two or more such elements. Each of thereferences identified herein is hereby incorporated by reference asthough fully set forth herein.

1. (canceled)
 2. An implantable neural interface system, comprising: abase insertable into a cranium and including a shelf; a neural interfacedevice coupled to the base, wherein the neural interface device includesan electrode array; an electronic component coupled to the neuralinterface device and including a circuit board on the shelf, wherein thecircuit board is substantially flat and defines an open center.
 3. Theimplantable neural interface system of claim 2, wherein the circuitboard is approximately circular.
 4. The implantable neural interfacesystem of claim 3, wherein the neural interface device comprises aneuroprobe assembly, and wherein the electrode array is coupled to theneuroprobe assembly.
 5. The implantable neural interface system of claim4, wherein the neuroprobe assembly comprises a penetrating electrode,and wherein the electrode array is disposed on the penetratingelectrode.
 6. The implantable neural interface system of claim 5,further comprising a plug that couples to the base and defines, on aside of the plug, a recess that houses at least a portion of theelectronic component.
 7. The implantable neural interface system ofclaim 4, wherein the neuroprobe assembly is a planar probe.
 8. Theimplantable neural interface system of claim 3, further comprising afluidic component.
 9. The implantable neural interface system of claim8, wherein the fluidic component includes at least one microchanneldefined in the neural interface device.
 10. An implantable neuralinterface system, comprising: a base insertable into a cranium anddefining a groove from a bottom portion of the base to a top portion ofthe base; a neural interface device coupled to the base, wherein theneural interface device includes an electrode array; an electroniccomponent coupled to the neural interface device; and a flexibleinterconnect cable that connects the electronic component to theelectrode array, wherein at least a portion of the flexible interconnectcable resides in the groove.
 11. The implantable neural interface systemof claim 10, wherein the neural interface device comprises a neuroprobeassembly, and wherein the electrode array is coupled to the neuroprobeassembly.
 12. The implantable neural interface system of claim 11,wherein the neuroprobe assembly includes a penetrating electrode, andwherein the electrode array is disposed on the penetrating electrode.13. The implantable neural interface system of claim 12, wherein thebase further includes a shelf and the electronic component includes acircuit board on the shelf within the base, wherein the circuit board issubstantially flat and circular and defines an open center.
 14. Theimplantable neural interface system of claim 10, wherein the neuroprobeassembly is a planar probe.
 15. The implantable neural interface systemof claim 10, wherein the electronic component includes a circuit boardplaced in the base.
 16. The implantable neural interface system of claim15, wherein the circuit board is flexible and placed on an inner wall ofthe base.
 17. An implantable neural interface system, comprising: a baseinsertable into a cranium; a neural interface device coupled to thebase, wherein the neural interface device includes an electrode array;an electronic component coupled to the neural interface device; and aplug that couples to the base and defines a recess that houses at leasta portion of the electronic component.
 18. The implantable neuralinterface system of claim 17, wherein the neural interface devicecomprises a neuroprobe assembly, and wherein the electrode array iscoupled to the neuroprobe assembly.
 19. The implantable neural interfacesystem of claim 18, wherein the neuroprobe assembly includes apenetrating electrode, and wherein the electrode array is disposed onthe penetrating electrode.
 20. The implantable neural interface systemof claim 19, wherein the base defines a groove from a bottom portion ofthe base to a top portion of the base, further comprising a flexibleinterconnect cable that connects the electronic component to theelectrode array, and wherein at least a portion of the flexibleinterconnect cable resides in the groove.
 21. The implantable neuralinterface system of claim 18, wherein the neuroprobe assembly is aplanar probe.